There are several here in Florida that are underwater. Off the top of my head, one you need scuba gear for, one you just need a snorkel. They do tend to get wet though. The Scuba one as a log book that is designed as a slate.

We are going up the East Coast for our family vacation this year (from FL) and this one was already on the to do list, along with several others that have massive favorite points. We can wait for the trip in July.

We just found one here in Florida that was in a graveyard and the cache was actually in a marble urn that had the Geocaching symbol on top of it. Very cool cache. I have a video of it somewhere, I will try and get it posted here so you can see it.